Protective system for electric circuits



Feb. 7, 1928.

' 1,658,329 P. w. FORSBERG PROTECTIVE SYSTEM FOR ELECTRIC CIRCUITS Filed Nov. 192s OWN! 0 /5 A? T 97 7 '7' O zz l 2:)" rrrag 1 2/ /3 I I I ym /5 a [71 0 m I o VI I 22 a 0 Inventor:

p t r W. Forsbe r.

by fly H i s Att or-n e y,

Patented Feb. 7, 1928.

UNITED, STATES fPATENT "OFFICE.

IPETER W. FORSBERG, 0F SCHENE CTADY, NEWYORK, ASSIGNDR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW'YORK.

PROTECTIVE SYSTEM FOR ELECTRIC CTRCUITS.

' Application filed November 3, 1925. Serial No. v66,619.

This invention relates to protective systems for electric circuits, and morev particularly to protective systems for electric circuits adapted to carry current either direction, and has for its object the provision of a novel arrangement of electro-responsive protective apparatus for preventing the flow of currents of abnormal value in either direction in the circuit.

.More specifically the invention provides an improved arrangement of ele'ctro-responsive circuit interrupting devices whereby a circuit of the above: character may be interrupted positively and quickly upon the occurrence of an abnormal overload condition such, for

example,-as a short circuitor ground when thecurrent is flowing in either direction in the circuit. I Although of general application, the present invention is particularly advantageous Patent- No.. 15,441, in the power circuit'of an' electric locomotive, in order to afford protection ,irom excessive rushes of current durmg motoring opcratlon which may cause destructive arcing or flash-over ,ofthe driving 7 motors. However, since the Tritle type of "fully set forth in the above Tritle applicahigh speed circuit interrupter employs a movable. circuit controlling member which is electromagnetically held in the circuit closing position, and is arranged to be released responsive'ly only to predetermined conditions ofcurrent fiowinone direction, and abnormal-condition occurring during regeneraon the high voltage-supply line may cause,

an equally disastrous arcing or flash-over of the motors against which no protection is A all'orded. 1

In accordance with ,my present invention this difficulty is overcome by means of a pair 7 of electro-responsive circuit protecting tde-' vices, such as the "Tri-tle high speed circuit,

[.nected in series in the circuit.

interrupter-s previously referred to, which are connected in series in the circuit and arranged m such manner that one interrupter to excessive how of motoring current in the circuit, while the other interrupter operates to open the circuit responsively only to excessive flow of regenerated current in-the circuit.

The invention will be better understood from the following description taken in connection with the accompanying drawing, in which the single figure dlagrammatically illustrates a protective system. for the power circuit of an electric locomotive embodying the invention.

Referring to the drawing, it will be seen that the power circuit of an electric locomotive extending from the high voltage trolley T to ground and including the direct current driving motors 10 is under the control of a pair ofelectro-responsive circuit controlling devices 11 and 12 which are con- It will be understood that the usual form of switch mechanism employed for connecting the driving motors 10 of the locomotive in series and in parallel, as well as the ordinary form of speed controlling resistors for the motors, have been omitted from the drawing for the sake of simplicity therein. As shown,

each of the electro-responsive circuit controlling-devices 11 and 12 is a high speed trip free circuit interrupter of the type described and claimed in the co-pending application.

of John F. Tritle,-Serial No; 511,100, filed October 28, 1921, and assigned to the same asslgnee as my present inventlon. As more tion,".the principal parts of the, circuit in terrupter 11, asillustrated in the drawing, comprise themovable switcharm 13, which operates to open the circuit responsivelyonly cooperates with the stationary contact 14 to open and close the power circuit of the loco- .i'motive. Switch arm 13, is pivoted inter mediate its ends in suitable bearings carried at one end of the movable magnetic member 15 which in turn is mounted to rotate about the stationary pin 16. A. common electromagnet 18. Theelectromagnet 18 is provided with a shunt holding Winding 19 for normally exerting sufficient magnetic attraction on the movable magnetic member 15 when the latter is operated into attractive relation with the poles of the electromagscribed and claimed in the Patent 'No. 1,- 606,483. -In the particular circuit interrupter illustrated the bucking bar or series winding 20 is connected to be energized re-v sponsively to the current in the power circult of the electric locomotive, and 1s shunted by an inductive shunt 21 having greater inductance than the inductance of the bucking bar orvseries winding 20, in order to effect opening oi the interrupter at a lower value of current upon a rapid increase or rush of current. The circuit interrupter 11 is oper ated to the closing positionby means of an electromagnetic closing mechanism f 22 which is arranged to be energized from the low voltage supply lines 23 under the control of the normally open push button 241. As illustrated, the holding winding 19 is connected'to receive current from the low voltage supply'lines 23 under the control of the normally closed push button 25. v

The circuit interrupter 12having the movable circuit controlling member 13,'n1ovable magnetic member .15, the holding electromagnet 18 and the other elements constructed and arranged in exactly the same manner as described in connection with in:

terrupter 11 is connected so that the circuit] controlling member 13" is in series with the circuit controlling member 13 of interrupter 'llrin the power circuit of the locomotive and the bucking bar or series winding '20 likewise is connected to be energized re sponsively to the current in the power circuit and is shunted by the inductive shunt 21. However, it will be observed that the holding winding19 is arranged to be energized from the low voltage supply lines 23' in a a reverse direction from the holding winding 19 of the interrupter 11. By this arrangement the magnetic reaction of the bucking bar or' series winding 20 upon the magnetic influence of the holding winding 19 of interrupter 12 is reversed from the magnetic influence of the bucking bar or series winding 20 upon the holding winding 19 of interrupter 11. In this way the in- 'terrupter 11 is arranged to be operated to the circuit opening position responsively only to predetermined conditions of'flow in the power circuit of the locomotive in one direction, while the interrupter 12 is arranged to operate to the circuit opening position responsively only to predetermined conditions of flow of current in the power circuit'of the locomotive inthe reverse direction. V Circuit interrupters 11 and 12 are electrically interlocked so that the automatic opening of either interrupter causes the subsequent opening of the other interrupter.

This is accomplished by means of the auxiliary switches 26 and 27, the former of which is mechanically connected to the movable switch arm 13 of the interrupter 11 and is arranged to control'the energizing circuit of;

the holding winding 19 of the interrupter 12, while the auxiliary'switch 27 is actuated by the swtch member'lS' of interrupter 12 and is connected to control the energizing circuit of the holding winding 19 of interrupter 11.

The operation of the protective system illustrated is as follows: With the high voltage trolley T and the low voltage supply lines 23 energized from suitable sources, the interrupters 11 and 12 may be closed to com: plete the power circuit ofthe locomotive by closure-of the normally open control switch 24. This simultaneously energizes the 010s ing mechanisms 22 and 22' and the resulting operation thereof moves the respective magnetic members 15 and 15 of the interrupters 11 and 12 into-attractive relation with the holding electromagnets 18 and 18. Upon the closure of the auxiliary switches 26 and 27 the holding windings 19 and 19 are energized 'toelectromagnetically hold the mag netic members 15 and 15 in the attractive 7 position. Switch 24 now may be released tov permitthe closure of'the circuit controlling member 13 and 13 by the biasing springs 17 andv 17 respectively.

With the interrupters 11 and 12 electromagnetically held in the closed position the driving motors 10 of the locomotive maybe controlled by a suitable switch mechanism,

of the locomotive. During motoring operanot shown in the drawing, to effect either 1 motoring or regenerative braking operation tion the interrupter 11 afi'ords automatic protection to the powercircuit of the locomotive against excessive rushes of overload current which might cause destructive arcingor fiash-o'verof the motors 10. Thus upon the occurrence of a rapidly increasing overload current during motoring operation the inductive shunt21 forces an increased proportion of the current into the buckling bar'or series winding 20 and the magnetic reaction otthe bucklingbaror series winding 20 upon the flux set up in the holding elec tromagnet 18 by the holdingwinding 19 'efiects the release of the magnet 15 and thereby permits the biasing spring 17 quick- 'ly to open the movable contact arm 13. Under these conditions, however, the mag;

netic reaction of the buckling bar or series reassess.

winding;=2(ll upon ytheflax in the holding winding 18 in interrupter 12 'wi-ll not effect: the release of the magnetic member 15" due to the fact that holding winding-19 isen= ergized in the reverse direction from the-a; holding winding 19. Upon the-openingbt interrupter'll the circuit of holding winding 19" is interrupted "by" the auxiliary-switch" mechanism 26 1 and the resultingv 'deenergiza tion of the holding =win'di1'1'g -;19 permits the interrupter 12 to open in accordance -with'its bias, Reclosure of the -interrupters-11' and 12 is accomplished in the manner previously-- described. i

During regenerative brakingoperationthe interrupter :12 aiiords protection-to the pow--- er circuit otthe locomotive againstexcessive rushes of overload current-since under -regenerative braking conditions current flows in the power circuit in the reverse direction. In this case the inductive shunt 21 forces an increased proportion of the current into the bucking bar or series winding and the magnetic reaction of the bucking bar or series winding 20 upon the flux in the holding electromagnet 18' is in the proper relation to efi'ectthe release of the magnetic member 15 and the consequent opening of the interrupter 12. The interrupter 11 is unresponsive to excessive overloads which occur during regenerative braking operation and is opened only when the energizing circuit of holding winding 19 is interrupted through operation of the auxiliary swi ch 27 upon opening of interrupter 12. Thus it will be seen that by arranging the interrupter 11 to operate responsively to a rapid increase in the flow of current in the circuit in one direction and the interrupter 12 to operate responsively to a rapid increase in the flow of current in the other direction, the power circuit of the locomotive is protected against excessive overloads during both motoring and regenerative braking operation.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. A protective system for an electric circuit arranged to carry current in either direction comprising a pair of independently operable high speed electro-responsive circuit interrupters connected in series relation in the circuit and each arranged to operate separately to open the circuit responsively to a rapid increase in the flow of current in the circuit in a different direction.

2. A protective system for an electric circuit arranged to carry current in either direction comprising an electro-responsive circuit interrupter connected in the circuit and arranged to operate to open the circuit responsively only to flow of current in the circuit in one direction, and an independently operable electro-responsive circuit interrupter connected in the controlled circuit in series with the first device and arranged to operate to open the circuit aresponsively only-v to flo'w of current:1nzthezclrcuit'lnitheireverser direction; and means whereby the; operation 01 one--:oti said devices causes-the isubsequentr operation of the other device;

8.:A protective system for. an .zelectri'cflclre: cuit arrangedto carry currentp'in either..,d1- i rection comprising ahigh; speed: 'GIGCtIO-IGE? sponsive circuit interrupter having r a :move: able switch"member:connected. in then-con:

trolled: circuit and arranged to .:be;. electnomagnetically held in: the circuiteclosing pos. sitiomand operated to wopenrthe .ClICu'lG :re-e sponsively to a .fiownofxicurrent .ot :predeter:-:

minedivaluerinxone directioniand toibe op-:;

eratedi to. open'the. circuit atra 101Ve1;V3;lll6 of currentnupon rapidzincrease dmthe flows or" current v in ath'e circuit; :in 1 said. oneudirlec-i tion; and a ;second :high speed: electro-erespone sive circuit interrupter having a switch member connected in the controlled circuit in series with said first member and arranged to be electromagnetically held in the circuit-closing position and operated to open the circuit responsively to a flow of current of predetermined value in the reverse direction and to be operated to open the circuit at a lower value of current upon a rapid increase in the flow of current in the circuit in said reverse direction;

4. A protective system for an electric circuit arranged to carry current in either direction comprising a high speed circuit interrupt-er having a movable switch member connected in the controlled circuit and biased to the circuit opening position, the said switch member being arranged to be electromagnetically held in the circuit closing position under the joint magnetic influence of a holding winding and a conductor asso- 1 ciated therewith and connected to be energized responsively to the current in the controlled circuit to effect the quick release of the switch member responsively only to predetermined conditions of current flow in the circuit in one direction, and a second high speed circuit interrupter having an independently movable switch member connected in the controlled circuit in series with the said first movable switch member of the first interrupter and biased to the circuit opening position, the said second switch member being arranged to be electromagnetically held in the circuit closing position under the joint magnetic influenceof a holding winding and a conductor associated therewith and connected to be energized responsively to the current in the controlled circuit to efiect the quick release of the said second independently movable switch member responsively only to predetermined conditions of current flow in the circuit in the reverse direction.

5. A protective system for an electric circuit arranged to carry current in either direction comprising a high speed circuit interrupterha ving a movable switch member connected in the controlled circuit and biased to the circuit opening position, the said switch member being arranged to be electro- V circuit in series with the said movable switch 7 magnetically held, in the circuit closing position under the joint magnetic influence of a holding winding and a conductor associated therewith and connected to .be energized responsively to the current in the conmember of the first interrupter and biased to the circuit opening position and arranged to be electromagnetically held in the circuit closing position under the joint magnetic in-.

fiuence'of a holding winding and a'conductor associated therewith and connected to be energized responsively to the current in the controlled-circuit to: eflect the quick release of the said second movable switch member responsively only to predetermined conditions of current flow in the circuit in the reverse direction, and switch mechanism, and connections whereby the operation of the switch member of either interrupter to the circuit opening position interrupts the energizing circuit of the holding winding of the other interrupter to release the corresponding switch member to operate to thercircuit' opening position in accordance with its bias. In: witness whereof, I have hereunto set my hand this 20th day of October, 1925.

PETER W. FORSBERG. 

